Carbon Fiber-reinforced Polymer Composite Materials Research Articles

Examination of Mechanical Tests of CFRP Composite Material with Different Orientation Angles Used in the Automotive Industry

Carbon fiber reinforced polymer (CFRP) composites, which have good mechanical properties, are widely used in many sectors today. Carbon fabrics/epoxy composites are materials used in the production of various components in many professional in-dustries such as aerospace, construction, textile and automotive. The use of CFRP composite lightweight materials has begun to increase in the automotive industry to reduce emissions, increase crash resistance and save fuel. In order to evaluate mate-rials in these industrial areas, it becomes important to know their mechanical proper-ties such as tensile strength and three-point bending. In this study, carbon fiber rein-forced polymer (CFRP) [0°/0°], [0°/90°], [±45°] and [0°/90°/+45°/-45°/-45°/+45°/90°/0°] four different types of orientation CFR materials were used.Tensile and three-point bending tests were performed on the samples produced with 4 differ-ent orientation angles. Three-point bending tests were carried out in accordance with ASTM D7264 standards and tensile tests were carried out in accordance with ASTM D 3039 standards. Stress-strain and force-strain curves were drawn. It has been ob-served that the material type that withstands the maximum force the most is the C48 structured CFRP material with an 8-layer [0°/90°/+45°/-45°]s arrangement. However, it was concluded that the carrying capacity of the C48 sample was higher than the samples with different fabric orientation.

EFFECT OF LOW-VELOCITY IMPACT DAMAGE ON THE ELECTROMAGNETIC INTERFERENCE SHIELDING EFFECTIVENESS OF CFRP COMPOSITES

Carbon fiber reinforced polymer (CFRP) composites are widely used engineering materials in aerospace technologies. These electrically conductive carbon-based materials, due to the lightness advantages, are preferred as shields against electromagnetic radiation, especially in aircraft and satellites. However, the performance losses caused by damage because of flying object collision such as bird, hail, or projectile contain significant uncertainty. Herein, the CFRP composite material was structurally damaged by low velocity impact test set-up at various energy levels between 2.5 to 10 joules, and then its electromagnetic interference (EMI) shielding performance was investigated. In addition, the electrical properties of the material were also examined, and the occurred damage status was evaluated by microscopy studies. Intrinsically, the increase in impact energy increases the grade of damage on body of the material. This results in a drastic decrease in electrical conductivity and EMI performance. In experiments, where 5 joule energy is detected as a threshold level, it has been observed that irreparable damage occurs at energy levels above this value.

Fabrication and Experimental Investigation of Composite Pressure Vessel

Abstract: Composite pressure vessels are an important type of high-pressure containers that are widely used in aerospace industries. The pressure vessels develop hoop stresses that are twice the longitudinal stresses. CFRP (Carbon Fiber Reinforced Polymer) composite materials with their higher specific strength and characteristics will result in reduction of weight of the structure when compared with isotropic materials like steel. The present work is aimed in understanding the behaviour of the Composite Pressure Vessel with variation of internal pressure. In this connection, a pressure vessel using CFRP (Carbon Fiber Reinforced Polymer) is fabricated which can hold liquids or gases under pressure and is tested at various pressures. The FEA tool ANSYS 14.5 is used to determine better fiber angle required for liquid storage, when the conventional low carbon steel cylinder is replaced with CFRP Pressure Vessel.

Aluminum and Carbon Fiber Reinforced Polymer Composite Material Comparative Strength Analysis of a Structural Part in F-16 Fighter Aircraft Landing Gear

In this study, the geometric structure, weight and boundary conditions of the aluminum alloy main landing gear FS 34.180 structural part currently used in F-16 fighter aircraft are determined. Finite element (FE) analysis is performed considering the forces that the existing part is exposed to in four different scenarios with Ansys Workbench software. Then, a FE model of the same part is created from carbon fiber reinforced polymer (CFRP) composite material. The loading conditions applied in the four scenario are also applied to the new CFRP composite material model. Equivalent stress, equivalent total strain, maximum shear stress and total deformation values in the models created with both materials are calculated.
 The results obtained for both materials are compared. As a result of the comparison, it is observed that there is a decrease of approximately 0.8% in the equivalent stress, 12% in the equivalent total strain, 0.7% in the maximum shear stress and 11.8% in the total deformation values for the same loading and boundary conditions. In addition, the total mass of the part is reduced from 31.17 kg to 20.77 kg, which corresponds to a reduction of 33.37%. 
 This development is expected to reduce the weight of the aircraft as well as extend the fatigue life and maintenance period.

High frequency eddy current inspection of fibre placement in Carbon Fibre Reinforced Polymer Composites

This paper presents experimental and simulation studies of high frequency eddy current non-destructive testing (NDT) methods for inspection of carbon fibre reinforced polymer (CFRP) composites. It is well known that CFRP composite materials are widely used in industry as structural components, and products based on such materials are increasingly developed and introduced to market. In recent years, non-conventional eddy current method operating at high frequencies for NDT of composites begins to attract attention. It provides a non-contact, couplant-free option of inspection when compared with the other NDT methods currently used in industry. As eddy current relies on fibre fabrics in individual plies to form the current pathways, the eddy current paths in composite are unsurprisingly complex due to the structural features of composite laminates when compared with that in homogenous conducting metals for which conventional eddy current NDT is often used in industry. It will be noted that the knowledge is still limited so far about the eddy current distributions in composite laminates due to lack of effective theoretical and numerical models. This paper will focus on the development of a new numerical model that is suitable for use in simulations of high frequency eddy current inspection of fibre placements. An effective model is desirable for understanding the performance dependence of the eddy current testing method on the material properties, composite structural features, and other parameters involved. In this model, the fibre tow layout of individual plies is taken into consideration. The collection of the pickup signals by the sensor probe shows clear images of the fibre placement in different layers. The simulation results are compared with experimental results of fibre placement imaging. The model is useful for understanding the physical process for inspection of composites using high frequency eddy current methods, and for studying the influence of the controllable parameters involved.

Analysis of surface integrity in drilling carbon fiber reinforced polymer composite material under various cooling/lubricating conditions

Carbon Fiber Reinforced Polymer (CFRP) composite materials are a class of advanced materials widely used in versatile applications, including aerospace and automotive industries, due to their exceptional physical and mechanical properties. Owing to the heterogeneous nature of the composites, it is often a challenging task to machine them unlike metals. Drilling in particular, the most commonly used process for component assembly, is critical especially in the aerospace sector that demands parts of highest quality and surface integrity. Conventionally, all composites are machined under dry conditions. While there are drawbacks related to dry drilling, for example, poor surface roughness, there is a need to develop processes that yield good quality parts demonstrating improved surface integrity. This study aims at investigating the machining performance when drilling CFRP composite material under cryogenic (Cryo), minimum quantity lubrication (MQL) and hybrid (CryoMQL) conditions and comparing the performance with dry drilling in terms of the thrust force, torque, delamination, geometric error such as diametric variation, and surface integrity assessment including average surface roughness, hardness and sub-surface damage analysis. Additionally, the effects of varying the feed on the drilling performance were examined. Based on the results, it was concluded that drilling of CFRP composite material using coolant/lubricant outperformed dry drilling by producing better quality parts. Also, varying the feed proved to be advantageous over drilling at constant feed.

Shear and flexural strengthening of reinforced concrete beams with variable compressive strength values using externally bonded carbon fiber plates

This paper presents experimental and analytical research to study the shear and flexural performance of Reinforced Concrete (RC) beams strengthened using two types of externally bonded Carbon Fiber Reinforced Polymer (CFRP) composites; including laminates and sheets. A total of 24 full-scale RC beams were tested up to failure. Concrete compressive strengths of 17, 32, and 47 MPa were used, with CFRP composites attached in six different configurations in an effort to optimize the flexural and shear load-carrying capacities of the specimens tested. Results showed that externally bonded CFRP composites considerably improved both the shear and flexural strengths of the beams. Notably speaking, the effectiveness of the CFRP composite material was inversely proportional to the concrete compressive strength. Significant improvement of the shear strength ranging from 28.9% to 29.6% was observed for beams with CFRP U-wraps compared to beams with laminate strips which ranged between 14.4% and 23.8% when the compressive strength was increased from 17 to 47 MPa. Meanwhile, those strengthened with half U-wraps had a notable improvement in their flexural strength (i.e., ultimate load carrying capacity) by a range of 22.4%–46.2%, as opposed to laminate strengthened beams that varied between 17.8% and 38.4% with increased compressive strength of the concrete mix. Finally, theoretical predictions using the ACI 440.2R-14 guidelines were compared to experimental results; however, the differences turned out to be relatively large due to the intrinsic empirical nature of the Code predicted equations.

Ultrasonic Evaluation of Porosity in Out-of-Autoclave Carbon Fiber–Reinforced Polymer Composite Material

Ultrasonic longitudinal wave propagation is studied in out-of-autoclave (OoA) carbon fiber–reinforced polymer composite material with varying levels of porosity contents. A combination of cure pressures and a solvent is used to produce specimens with void contents in the range of 0% to 22%. Ultrasonic measurements are made in through-transmission mode, and the data is processed to study various aspects of wave interaction with porosity in OoA specimens. The specimens with a wide range of void contents have enabled the study of broader trends of ultrasonic center frequency, wave velocity, and attenuation with respect to porosity. Results show ultrasonic center frequency and wave velocity are decreased linearly as the void content increases. The relationship of ultrasonic wave attenuation can be approximated by a logarithmic relationship when considering the full range of void content studied. Strength measurements of specimens with varying void contents are made using the flatwise tensile (FWT) test. It is observed that the strength rapidly decreases with increasing porosity. Correlations made between FWT strength, ultrasonic wave velocity, and attenuation are best described by logarithmic relationships. The data shows a potential for inferring strength knockdowns due to the presence of porosity based on ultrasonic measurements.

Effect of build orientation and raster pattern on the fracture behavior of carbon fiber reinforced polymer composites fabricated by additive manufacturing

Additive manufacturing (AM) process parameters highly affect the mechanical and fracture properties of additively manufactured carbon fiber reinforced polymer (CFRP) composites. In this work, we study the effect of two process parameters, including build orientation (XYZ, XZY, and ZXY) and raster pattern ( ± 45º and 0º/90º), on the fracture behavior of the CFRP composites fabricated by fused filament fabrication (FFF). The mode I fracture toughness and effective fracture energy of the CFRP composite materials are measured on compact tension samples. The crack growth direction in the FFF-fabricated CFRP composites is found to be controlled by both build orientation and raster pattern. The fracture toughness of the examined CFRP material is sensitive to build orientation, while the effective fracture energy reveals significant dependence on both build orientation and raster pattern. The samples fabricated with the XYZ and ZXY build orientations exhibit 5-fold greater effective fracture energy than the ones with the XZY build orientation. A wide range of fracture energy dissipation mechanisms, including fiber-bridging and fiber pull-out, are identified depending on the process parameters. The reported fracture trends in this study have the potential to provide guidelines for the development of FFF-fabricated CFRP composites with high fracture resistance.

Carbon-fiber reinforced polymer composites: A comparison of manufacturing methods on mechanical properties

Carbon-fiber reinforced polymer composite materials are used throughout industry for their excellent mechanical properties; in particular, these composites boast high specific stiffnesses and specific strengths. However, current limitations on manufacturing, which vary greatly based on the technology that is utilized, restrict access to composite materials in a variety of applications. Traditional wet hand-layups offer a large diversity of viable constituent materials, but the fabrication geometry is limited and the manual process is time-consuming. In contrast, fiber 3D-printing (F3DP) allows for the production of complex geometries and requires little manual labor. In this study, laminates with continuous carbon fiber reinforcement printed using a commercially-available 3D printer are compared to carbon fiber fabric-resin composites produced using manual layup techniques. Cross-ply [0,90,0,90,0]T laminates were fabricated and subject to mechanical testing in uniaxial tension and flexure. After normalization with respect to fiber volume fraction, we found that the tensile strength and stiffness of cross-ply carbon fiber composites manufactured using F3DP were higher than the tensile strength and stiffness of cross-ply specimens manufactured by a traditional hand-layup method; however, the hand-layup specimens exhibited higher strength and stiffness in flexure. The difference in material properties evident between the two fabrication methods suggests that each has its own suitable application. We anticipate that further studying the failure response of printed, fiber-reinforced composite materials to various loading modalities will give insight into potential areas of improvement for F3DP material selection and printing processes, particularly relating to void reduction. On a broader scale, comparing and analyzing the mechanical properties of composite laminates produced in these various methods will provide perspective on the viability of novel additive manufacturing methods for large-scale production and industrial applications.

Numerical micromechanics model of carbon fiber-reinforced composite using various periodical fiber arrangement

A numerical model of unidirectional carbon fiber-reinforced polymer composite material at the micro-level has been introduced to complement the experiment and analytical model in estimating the elastic properties of composite material. Idealization was performed in the model by using a periodically distributed fiber following square and hexagonal packing arrangement. The determination of the unit cell configuration was made by considering the periodic boundary condition associated with the selected configuration. The idealization using periodic fiber arrangement was proved to adequately estimate the elastic properties of composite material. The hexagonal model was proved to solve the drawbacks of the square model in estimating the shear properties with error reduction up to 50 % in comparison to the square model.

Linear-Nonlinear Stiffness Responses of Carbon Fiber-Reinforced Polymer Composite Materials and Structures: A Numerical Study.

The stiffness response or load-deformation/displacement behavior is the most important mechanical behavior that frequently being utilized for validation of the mathematical-physical models representing the mechanical behavior of solid objects in numerical method, compared to actual experimental data. This numerical study aims to investigate the linear-nonlinear stiffness behavior of carbon fiber-reinforced polymer (CFRP) composites at material and structural levels, and its dependency to the sets of individual/group elastic and damage model parameters. In this regard, a validated constitutive damage model, elastic-damage properties as reference data, and simulation process, that account for elastic, yielding, and damage evolution, are considered in the finite element model development process. The linear-nonlinear stiffness responses of four cases are examined, including a unidirectional CFRP composite laminate (material level) under tensile load, and also three multidirectional composite structures under flexural loads. The result indicated a direct dependency of the stiffness response at the material level to the elastic properties. However, the stiffness behavior of the composite structures depends both on the structural configuration, geometry, lay-ups as well as the mechanical properties of the CFRP composite. The value of maximum reaction force and displacement of the composite structures, as well as the nonlinear response of the structures are highly dependent not only to the mechanical properties, but also to the geometry and the configuration of the structures.

ВЛИЯНИЕ СВЧ ЭЛЕКТРОМАГНИТНОГО ПОЛЯ НА ТВЕРДОСТЬ АРМИРОВАННОГО ВОЛОКНАМИ УГЛЕПЛАСТИКА С РАСПРЕДЕЛЕННОЙ В ПОВЕРХНОСТНОМ СЛОЕ МОЛНИЕЗАЩИТНОЙ СЕТКОЙ

Based on the analysis of scientific and technical literature and trends in the development of multi-purpose aircrafts, we can see a steady extension of the use of polymer composite materials (PCM) in their design. The importance of lightning protection is noted for aircrafts, the skin of which consists mainly of the PCM, and it is shown that one of the common means is a lightning protection coating (LPC) in the form of a metal grid distributed in the PCM surface layer. Anisotropy of PCM properties and reduced fracture toughness in comparison with metals necessitates the improvement of PCM compositions and technologies of their formation as well as the development of methods for final hardening treatment in the cured state, which can be effectively performed under the effect of microwave electromagnetic field. Consideration is given to the influence of a short-term exposure to microwave electromagnetic field on the stability of carbon fiber-reinforced PCM with PLC against impact loads, as well as on the surface hardness. Our findings show a decrease in the damaged area of the impact zone by 40-60% and the absence of microcracking and delamination as well as an increase in hardness by 7.8%. Particular emphasis is placed on a 3-fold decrease in the spread of hardness values after the microwave exposure, this indicating a significant increase in the uniformity of this important characteristic for the component performance. As a mechanism of these modifications, it is proposed to reduce the pore size and porosity and to increase the number of points of contact interaction between matrix and fiber agglomerates that ensure an increase in the structural density.

IMPACT OF HIGH VOLTAGE ELECTRIC DISCHARGES ON THE CURED POLYMER COMPOSITE MATERIALS, MODIFIED IN A MICROWAVE ELECTROMAGNETIC FIELD

Due to the widespread use of carbon fiber-reinforced polymer composite materials (PCM) in the structural elements of aircraft with a distributed surface layer of lightning-proof coating (MFP) in the form of metal grids to reduce the risk of lightning strikes and the possibility of increasing their strength characteristics by processing in the microwave electromagnetic field, the need to study the impact of this method of processing on the resistance of PCM to high voltage electrical discharges. The studies of the impact of the discharge voltage 180…200 kV on samples of PCM with the minimum wage and no minimum wage. It is established that pretreatment of samples of the cured polymer composite MW in a microwave electromagnetic field energy flux density (17…18)104 µw/cm2 does not degrade their molniezaschita characteristics and contributes to reducing the size of the damaged area up to 1.5 times. Samples processed in the microwave electromagnetic field without MSP do not have delaminations and burns in contrast to the control ones. The obtained results indicate the possibility of strengthening treatment in the microwave electromagnetic field of structural elements of carbon fiber distributed in the surface layer of the MSP in the form of a metal grid.

Evaluation of hygrothermal ageing in CFRP composite material using a non-destructive approach

Hygrothermal (HT) ageing is a major concern for polymer composites in aircraft structures. An aircraft gets inspected after certain flying hours/cycles consuming man-hours, money and time. For economic inspection, non-contact, Non-destructive Evaluation (NDE) techniques can prove to be effective. This study presents NDE approaches using three such techniques, namely, X-ray radiography, ultrasound, and infrared thermography for evaluation of HT-ageing in Carbon Fiber Reinforced Polymer (CFRP) composites. For accelerating the ageing, specimens were subjected to a hot water environment up to more than 1000 hours at [Formula: see text]C. It’s influence on different NDE parameters through each technique was investigated. Building on the findings, the effectiveness of these techniques for the evaluation of HT-ageing in CFRP has been demonstrated.

A Constitutive Model of High-Early-Strength Cement with Perlite Powder as a Thermal-Insulating Material Confined by Caron Fiber Reinforced Plastics at Elevated Temperatures.

A parabolic stress–strain constitutive model for inorganic thermal-insulating material confined by carbon fiber-reinforced polymer (CFRP) exposed to a surrounding elevated temperature was proposed in this paper. The thermal-insulating material used in this study was composed of high-early-strength cement (HESC) and perlite powder. The compression strengths of four kinds of perlite powder composition ratios of thermal-insulating materials cylindrical specimens which were confined by one, two, and three-layer CFRP composite materials were acquired. The experimental results showed that the compression strength was enhanced as the amount of perlite substitute decreased or as the number of CFRP wrapping layers increased. The Mohr–Columb failure criteria were adopted to predict the maximum compressive strength of CFRP-confined inorganic thermal-insulating material. The strain at the maximum compressive strength was found from the experimental results, and the corresponding axial strain at the maximum compressive strength in the constitutive model was determined from the regression analysis. Furthermore, the compressive strengths of the four different perlite composites of thermal-insulating materials were obtained when heating the specimens from ambient temperature to 300 °C. The compressive strength decreased with an increase in temperature, and a thermal softening parameter model was proposed; the thermal softening parameter was determined from the experimental maximum compressive strength at an elevated temperature. Combining the above two models, the constitutive model of HESC with perlite powder additive as a thermal-insulating material confined by CFRP under elevated temperature was proposed.

Potassium sodium niobate lead-free piezoelectric nanocomposite generators based on carbon-fiber-reinforced polymer electrodes for energy-harvesting structures

The ability to harvest energy from the aircraft body movement like vibration will rapidly advance the Internet of Things (IoT) for aerospace by supporting power to the IoT sensors. However, the design and development of carbon-fiber-reinforced polymer (CFRP) composites with a function such as piezoelectricity are difficult due to the conductivity of carbon. In this study, we prepare a lead-free piezoelectric nano-particle-dispersed epoxy resin with laminated CFRP prepregs in the upper and lower surfaces. A large electric field was applied by corona discharge which polarized the composite successfully. The output power of this piezo-resin/CFRP composite due to impact load was then measured. The resonant frequency and output power of the composite excited by bending vibration were also evaluated. In this study, approximately 0.8 μW/cm3 of power was generated by the impact tests and approximately 4 nW/cm3 of power was obtained by the bending vibration tests. The results suggest that the CFRP prepreg can be used as an electrode to develop CFRP composite materials with energy-harvesting performance. Such novel findings are promising for the fabrication of piezo-resin/CFRP composite generators, opening the door for the design and development of lightweight, robust, and efficient energy-harvesting structures.

Thermo-elastic behaviour of carbon-fiber reinforced polymer and the effect of adding nanoparticles at elevated heat intensity

Thermal stress development in materials could lead to structural failure in engineering applications. Carbon-fiber reinforced polymer composite (CFRP) have gained wide acceptance in the manufacturing industry. However, its thermo-elastic behaviour at elevated temperatures still remains an open question. Heat transfer analysis coupled with material layer-wise arrangement technique of the CFRP was implemented to investigate the thermo-elastic behaviour of these composites. A finite element model (FEM) was built and studied using COMSOL Multiphysics software. The heat energy applied in the simulation was sourced from a heat beam model. The deposited beam power was varied from 10 to 200W, and focused at the centre of the laminate (yp = 0.15 m). The laminates considered were made up of six layers with distinctly different stacking sequences. The thermal stresses and strains obtained from the finite element analysis were assessed to observe the material's behaviour when subjected to increasing thermal load. Results revealed that thermal stresses are intense along fiber-direction of the composite laminates. The CFRP material was found to give good thermo-elastic characteristics at lower deposited heat power, however, this was not the case for higher deposited heat power (e.g. 200 W). The anisotropic property of the laminate had a significant influence in managing the thermal stresses. The study was repeated for carbon fibers doped with nanoparticles of silicon carbide (CFSiC) and resin bonded glass fiber (RBGF). It was found that the results were distinctly different when compared with the CFRP laminate. CFSiC showed to exhibit an ehanced thermo-elastic behaviour, due to the high thermal stability of SiC nanoparticles in the composite.

Optimization of machining parameters for abrasive water jet drilling of carbon fiber-reinforced polymer composite material using Taguchi method

Purpose The aim of this paper is to optimize the machining parameters to obtain the smallest average surface roughness values during drilling of the carbon fiber-reinforced polymer (CFRP) composite material with abrasive water jet (AWJ) and analyze the damage of the delamination. Design/methodology/approach CFRP composite material had been fabricated having fiber orientations frequently used in the aerospace industry (0°/45°/90°/−45°). Three different stand-off distances (1, 2 and 3 mm), three different water pressures (1,800, 2,800 and 3,800 bar) and three different hole diameters (4, 8 and 12 mm) were selected as processing parameters. The average surface roughness values were obtained, and delamination damage was then analyzed using Taguchi optimization. Drilling experiments were performed using the Taguchi L27 orthogonal array via Minitab 17 software. The signal/noise ratio was taken into account in the evaluation of the test results. Using the Taguchi method, the control factors giving the mean surface roughness values were determined. Analysis of variance was performed using the experimental results, and the effect levels of the control factors on the average surface roughness were found. Findings It was found that water pressure and hole diameter had a higher effect on average surface roughness, while water pressure and stand-off distance were effective on delamination. Practical implications Owing to their excellent thermal and mechanical properties, the CFRP composite materials show greater potential for their applications in aircraft and aerospace industry. Originality/value The novel approach is to reduce cost and spent time using Taguchi optimization as a result of AWJ drilling the material in this fiber orientation ([0°/45°/90°/−45°]s, which is often used in the aerospace industry).

Width Effect of CFRP Strips on the Compressive Behavior of Plain Concrete Cylinders

Several experimental studies have been conducted to investigate the influence of fiber-reinforced polymer on confined columns. Most of these studies examine the effect of some variable parameters such as the spacing between strips, the number of layers, the initial strength of concrete and the degree of confinement. This paper is the result of an experimental study on the behavior of plain concrete cylinders (O160 × 320 mm) reinforced with carbon fiber-reinforced polymer (CFRP) layers. The main purpose of this work is to study the influence of strip width of CFRP composite used for reinforcement. Five series of tests were carried out under a cyclic and progressive axial compression loading to failure. Tests were carried out using a compression machine MCC8 of 3000 kN capacity with automatic data acquisition system. In this investigation, the stress–strain curves were plotted in order to determine the stress–strain relationships and to obtain the behavior of the concrete cylinders. In conclusion, it is evident that this study has shown an optimal configuration and an adequate distribution of CFRP composite materials to minimize the utilization of the latter and thus to use it to its ultimate strength and to carry out the ultimate limit state design as well.